1. Field of the Invention
The present invention relates to an image projection apparatus that is configured such that a screen is arranged on a device front side, a projection unit is arranged in a device lower portion, image light from the projection unit is emitted upward and is caused to reflect by a reflection mirror arranged in a device upper portion, and an incident angle at which the image light is projected on a rear surface of the screen is set to an acute angle to shorten a depth from the projection unit to the screen.
2. Description of the Related Art
In an image projection apparatus that includes a screen provided on a device front side and an optical element arranged in the device, a dust-proof enclosure structure for preventing dust from entering from outside is needed in an internal space in which image light passes. Conventionally, for example, an image projection unit forms an enclosure structure portion that includes a projection window through which the image light reflected from an aspherical mirror passes, and this enclosure structure portion, a screen provided on a cabinet front side, and a reflection mirror provided on a cabinet top surface form the dust-proof enclosure structure for a part through which the image light passes together with a rear design cabinet of the image projection apparatus. The rear design cabinet is part of the enclosure and does not have an opening such as a heat radiating hole. The rear side of the cabinet is partially depressed to provide a storing portion in which a main electric circuit chassis is stored. The lid of this storing portion has a plurality of heat radiating holes to have a cooling structure of releasing heat to the outside (for example, see Japanese Patent Application Laid-open No. 2007-219447).
In the above image projection apparatus, when it is needed to clean dust accumulated on the upper surface of the projection window arranged in the emission portion of the image projection unit, before the large rear design cabinet which holds a plate base chassis on which a main electric circuit board is mounted and in which a speaker unit is stored is removed, the surface of the projection window cannot be exposed. The large and heavy rear design cabinet needs to be removed and the base chassis is provided on the rear design cabinet side, so that when removing the rear design cabinet, a connection cable with the image projection unit needs to be disconnected or be a sufficiently long cable.
Moreover, after removing the rear design cabinet, the screen provided on the cabinet front side, the reflection mirror provided on the cabinet top surface, and the like are exposed, so that dust from outside enters the inside of the cabinet while cleaning the projection window of the image projection unit in some cases. Furthermore, the main electric circuit chassis is stored in the storage recess portion on the cabinet rear side and a plurality of heat radiating holes is provided in the lid of this storing portion to have the cooling structure for releasing heat to the outside, so that airflow for cooling the main electric circuit chassis cannot be sufficiently secured. Moreover, a light collecting portion at which the image light crosses before being reflected by the reflection mirror provided on the top surface of the cabinet is spaced from the image projection unit, so that the size of the projection window needs to be made large, which results in increasing the cost.